Reconstruction of Abel-transformable images: The Gaussian basis-set expansion Abel transform method

Dribinski, V.; Ossadtchi, Alexei; Mandelshtam, Vladimir A.; Reisler, H.

doi:10.1063/1.1482156

Cited by 866 publications

(739 citation statements)

References 17 publications

(16 reference statements)

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“…Each image is used to reconstruct a three-dimensional scattering distribution using an inverse Abel transformation. 39 The speed distributions, P Cl (V), of the Cl fragments are extracted by integrating the threedimensional velocity distributions over all solid angles at each speed. Using momentum conservation and the appropriate Jacobian, the center of mass recoil translational energy distributions P(E T ) from the photodissociation are derived from the Cl speed distributions.…”

Section: Resultsmentioning

confidence: 99%

Determination of the Barrier Height for Acetyl Radical Dissociation from Acetyl Chloride Photodissociation at 235 nm Using Velocity Map Imaging

et al. 2008

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This work uses velocity map imaging to determine the barrier height for acetyl radical, CH 3 CO, dissociation to CH 3 + CO. Photodissociation of acetyl chloride at 235 nm generates acetyl radicals with an internal energy distribution spanning this barrier. We determine the velocity and internal energy distribution of all nascent acetyl radicals, stable and unstable, by measuring the velocities of the Cl( 2 P 3/2 ) and Cl( 2 P 1/2 ) cofragments. These Cl cofragments are detected with 2 + 1 resonance-enhanced multiphoton ionization (REMPI) in a spin-orbit branching ratio Cl( 2 P 3/2 ):Cl( 2 P 1/2 ) of 3.3 ( 0.2. Using 157 nm photoionization, we then detect the recoil velocities of the energetically stable acetyl radicals. The radicals and momentum matched Cl atoms evidence parallel angular distributions. Comparison of the total recoil translational energy distribution P(E T ) for all radicals to that obtained from the detection of stable radicals yields an onset for dissociation at a translational energy of 25.0 ( 0.4 kcal/mol. From this onset we can calculate the barrier height for CH 3 CO f CH 3 + CO, but this relies on prior determinations of the C-Cl bond energy of acetyl chloride. Using an experimental bond dissociation energy of 83.4 ( 0.2 kcal/mol yields a dissociation barrier of 14.2 ( 0.5 kcal/mol. Our data evidence that a portion of the acetyl radicals formed with total internal energy above the barrier are stable due to the partitioning of energy into rotation during the C-Cl bond fission of the precursor. Thus, the internal energy onset for dissociation is not as sharp as was assumed in prior determinations of the barrier. The experimentally determined onset is compared with that predicted from electronic structure calculations at the G3//B3LYP and CCSD(T) levels of theory.

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Section: Resultsmentioning

confidence: 99%

Determination of the Barrier Height for Acetyl Radical Dissociation from Acetyl Chloride Photodissociation at 235 nm Using Velocity Map Imaging

et al. 2008

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“…21 The Integrated photoelectron images are symmetrized to account for detector inhomogeneities and converted into three-dimensional momentum distributions by standard methods. 22 From these, photoelectron kinetic energy (eKE) and angular distributions are readily obtained. In many of the spectra shown here, one observes broad features with maximum intensity at kinetic energy eKE max ; these features are characterized by their vertical detachment energy, VDE, defined by VDE ) hν probe -eKE max .…”

Section: Methodsmentioning

confidence: 99%

Dynamics of Electron Solvation in Molecular Clusters

Ehrler

Neumark

2009

Acc. Chem. Res.

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S olvated electrons, and hydrated electrons in particular, are important species in condensed phase chemistry, physics, and biology. Many studies have examined the formation mechanism, reactivity, spectroscopy, and dynamics of electrons in aqueous solution and other solvents, leading to a fundamental understanding of the electron-solvent interaction. However, key aspects of solvated electrons remain controversial, and the interaction between hydrated electrons and water is of central interest. For example, although researchers generally accept that hydrated electrons, e aq -, occupy solvent cavities, another picture suggests that the electron resides in a diffuse orbital localized on a H 3 O radical. In addition, researchers have proposed two physically distinct models for the relaxation mechanism when the electron is excited. These models, formulated to interpret condensed phase experiments, have markedly different time scales for the internal conversion from the excited p state to the ground s state.Studies of negatively charged clusters, such as (H 2 O) n -and I -(H 2 O) n , offer a complementary perspective for studying aqueous electron solvation. In this Account, we use time-resolved photoelectron spectroscopy (TRPES), a femtosecond pump-probe technique in which mass-selected anions are electronically excited and then photodetached at a series of delay times, to focus on time-resolved dynamics in these and similar species. In (H 2 O) n -, TRPES gives evidence for ultrafast internal conversion in clusters up to n ) 100. Extrapolation of these results yields a p-state lifetime of 50 fs in the bulk limit. This is in good agreement with the nonadiabatic solvation model, one of the models proposed for relaxation of e aq -. Similarly, experiments on (MeOH) n -up to n ) 450 give an extrapolated p-state lifetime of 150 fs.TRPES investigations of I -(H 2 O) n and I -(CH 3 CN) n probe a different aspect of electron solvation dynamics. In these experiments, an ultraviolet pump pulse excites the cluster analog of the charge-transfer-to-solvent (CTTS) band, ejecting an electron from the iodide into the solvent network. The probe pulse then monitors the solvent response to this excess electron, specifically its stabilization via solvent rearrangement. In I -(H 2 O) n , the iodide sits outside the solvent network, as does the excess electron initially formed by CTTS excitation. However, the iodide in I -(CH 3 CN) n is internally solvated, and both experimental and theoretical evidence indicate that electrons in (CH 3 CN) n -are internally solvated. Hence, these experiments reflect the complex dynamics that ensue when the electron is photodetached within a highly confined solvent cavity.

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“…The positions of photoelectrons were recorded by a charge-coupled device (CCD) camera and one image data was obtained by accumulating 50000−100000 laser shots. The original 3D distribution was reconstructed using the Basis Set Expansion (BASEX) inverse Abel transform method, 50 and the photoelectron spectrum and the anisotropy parameters of transition bands were acquired by calculations based on one central slice of the 3D distribution. The spectrometer was calibrated using the spectra of Ag − and Au − at 355 nm.…”

Section: Methodsmentioning

confidence: 99%

Structure and Bonding in MPb₅^– (M = Cu, Ag, and Au): A Combined Investigation by Theoretical Calculations and Photoelectron Imaging Spectroscopy

et al. 2013

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Bimetallic clusters of MPb 5− (M = Cu, Ag, and Au) have been studied using density functional theory and photoelectron imaging spectroscopy. These anionic clusters and their neutrals were determined to be a Pb 5 trigonal bipyramid with the coinage metal atom on its triangular facet. This structure of each MPb 5 − or MPb 5 was found to be more than 0.5 eV lower than other structural candidates and that of each

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Reconstruction of Abel-transformable images: The Gaussian basis-set expansion Abel transform method

Cited by 866 publications

References 17 publications

Determination of the Barrier Height for Acetyl Radical Dissociation from Acetyl Chloride Photodissociation at 235 nm Using Velocity Map Imaging

Determination of the Barrier Height for Acetyl Radical Dissociation from Acetyl Chloride Photodissociation at 235 nm Using Velocity Map Imaging

Dynamics of Electron Solvation in Molecular Clusters

Structure and Bonding in MPb₅^– (M = Cu, Ag, and Au): A Combined Investigation by Theoretical Calculations and Photoelectron Imaging Spectroscopy

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Reconstruction of Abel-transformable images: The Gaussian basis-set expansion Abel transform method

Cited by 866 publications

References 17 publications

Determination of the Barrier Height for Acetyl Radical Dissociation from Acetyl Chloride Photodissociation at 235 nm Using Velocity Map Imaging

Determination of the Barrier Height for Acetyl Radical Dissociation from Acetyl Chloride Photodissociation at 235 nm Using Velocity Map Imaging

Dynamics of Electron Solvation in Molecular Clusters

Structure and Bonding in MPb5– (M = Cu, Ag, and Au): A Combined Investigation by Theoretical Calculations and Photoelectron Imaging Spectroscopy

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Structure and Bonding in MPb₅^– (M = Cu, Ag, and Au): A Combined Investigation by Theoretical Calculations and Photoelectron Imaging Spectroscopy